Heat exchanger



H. E. MEANS HEAT EXCHANGER May 26, 1964 Filed June 20, 1962 FIC: I

INVENTOR HERBERT E- MEANS ATTORNEY United States Patent ()1 3,134,432HEAT EXfil-EANGER Herbert E. Means, Wetherstield, Conn, assiguor toUnited Aircraft (Zorporation, East Hartford, Comm, a corporation ofDelaware Filed lane 20, 1962, Ser. N 293,857 19 Claims. {$1. 165-161)This invention relates to heat exchangers and more specifically to heatexchangers of counter-fluid-flow configuration suitable forhigh-temperature liquid-metal applications.

Among the objects of this invention are to provide a heat exchanger ofthis type in which the wall-to-wall spacing of the tubes in the centerportion of the tube matrix can be optimized independently of structurallimitations in the tube sheet; in which the unit is essentiallysymmetrical about both the axial and the mid plane center lines; inwhich the tubes in the tube matrix are all the sme length and the sameshape; in which a one-piece cylindrical shell can be assembled over thetube bundle, thereby eliminating longitudinal closure welds in the outercasing following assembly; in which the distribution of shell-side fluidis very good due to tube symmetry and due to tube fanning in the two endregions; in which no part of the main heat'exchanger structure, otherthan the tubes, has hot liquid on one side and cold liquid on the otherside; and in which the annular tube sheets can be reinforced andsupported at their center, thereby minimizing the tube sheet thickness.

A further object of this invention is to provide a heat exchangerespecially adapted for use with liquid metals which, when properlyinstalled, will completely fill Without trapping gas and completelydrain without liquid residue.

A still further object is generally to improve counterfluid-ilow heatexchangers for high-temperature liquidmetal applications.

These and other objects and advantages of the invention will be evidentor will be specifically pointed out in connection with the followingdetailed description of one embodiment of the invention shown in theaccompanying drawing. In the drawing:

FIG. 1 is a longitudinal sectional view of a preferred embodiment of theinvention;

FIG. 2 is a sectional view on line 22 of FIG. 1;

FIG. 3 is an enlarged sectional view on line 33 of FIG. 1;

FIG. 4 is an enlarged sectional View on line 4-4 of FIG. 1; and

FIG. 5 is a detail of a tube supporting ring.

As herein shown, the heat exchanger includes an axial tube bundle whichis generally cylindrical. As shown most clearly in FIG. 1, the tubebundle includes a cylindrical, intermediate portion 12 in which straighttubes are relatively closely spaced one from another. The straight tubesof the intermediate portion 12 have their ends fanned at 14 into short,straight, cylindrical end portions 16. Tubes in end portions 16, due tothe larger diameter of these end portions, are more widely spaced onefrom another than the tubes in the intermediate portion 12 which allowsvariation of the wallto-Wall tube spacing in portion 12 by variation ofthe spacing in end portions 16.

The tube bundle includes two tube sheets 18 and 2-8, one at each end,having apertures into which the ends of the tubes project. The spacingof the tube apertures in the tube sheets and the amount of fanningdetermines the spacing of the tubes in the tube bundle. The tube sheets18 and 26 have axial apertures 22 and 24, respectively, whichcommunicate with reentrant axial 3,134,432 ?atented May 25, 1964 "icechambers 26 and 28 formed at the ends of the tube bundle by reason ofthe fanned tube portions 14. It will be evident that by farming thetubes so that the tubes in the cylindrical end portions 16 can be morewidely spaced where they enter the tube sheets, it is possible toprovide any desired spacing or" the tubes in the intermediate portion 12to obtain the optimum axial flow characteristics through the long,straight, intermediate tube portion 12 of the tube bundle.

It will be apparent that the tube bundle is generally cylindrical and issymmetrical about both its longitudinal axis and its mid-plane centerline. Also, the tubes are identical in length and shape. Because of thecylindrical shape of the tube bundle, a one-piece cylindrical shell, orcasing, 30 can be assembled axially over the tube bundle, thus avoidingundesirable longitudinal closure welds iri the outer casing followingassembly.

A somewhat torus-shaped inlet header 32 is welded at its outer peripheryto one end of casing 36 and forms a closure for the casing at this endexcept for the central axial wall 34 of the header which is a close litin the aperture 24 of'the tube sheet and is welded tl1ere to. A radialinlet pipe 36 is provided for the tube side fluid flow. An axial outlettube 38 is welded to the inner end of wall 34 of the inlet headeradjacent the aperture 24 in the tube sheet which provides an outletpassage for the shell side fluid flow.

A similar outlet header 44 is provided at the other end of the shell 31)having a radial outlet pipe 42 for the tube side fluid and an axialinlet pipe 44 for the shell side fluid. As shown in FIG. 1, the inletpipe 44 and the out et pipe 38 for the shell side fluid flow are eachprovided with an annular flange 46 of semicircular cross section whichis welded at the junction of the headers and the tube sheets to providea small spacing 43 between these pipes and their respective headers.

A flow directing liner 5% is provided in order to insure that the fluidentering through pipe 44 into chamber 26 will flow along the straight,closely spaced, intermediate portion of the tubes. This liner iscylindrical over the straight tube portion 12 and has oblique flanges 52at its ends which engage the inner wall of the outer shell 3t adjacentend portions 16 of the tubes.

As shown, the straight intermediate portion of the tubes in the tubebundle are supported at spaced .points by a series of split hoops, orC-rings, 54. The outermost hoop has external lugs 55 welded theretowhich engage the straight-cylindrical, intermediate portion of the flowliner. The rest of the hoops 54 are provided with tube supports whichare welded thereto and are located between each pair of tubes about thehoop.

69 are staggered in the sets relative to adjacent tubes so as to provideadequate support for all of the tubes.

One set of hoops is shown in detail in FIG. 4.

The heat exchanger has been shown with its longitudinal axis in ahorizontal position to facilitate illustration and it may in someapplications be installed in this horizontal position. One of theadvantages of the heat exchanger of the present invention, however, isrealized only if it is installed with its longitudinal axis vertical. Itwill be noted that the inlet pipe 36 and the outlet pipe 42 for thetube-side flow are tangential to the semi-circular wall of the headersas these are viewed in cross-section in FIG. 1. As a result, whenvertically installed it is possible to completely fill the heatexchanger without trapping gas and to completely drain it without liquidresidue. This is of particular importance when one or both of the fluidsemployed are high temperature liquid metals, such as sodium, NaKlithium, etc.

It will be evident that as a result of the above construction a heatexchanger of the counter-fluid-flow type has been provided which isextremely simple to construct and which avoids many of the difiicultiesencountered in previous heat exchangers. For example, the elimination oflongitudinal welds in the outer casing, or shell, following assemblyenables the tube matrix to be accurately fitted into the casing withoutsubsequently distorting the shell due to the weld or setting'up stressesin the structure. Also, the arrangement by which the tubes are fannedadjacent their ends into a larger diameter section at the tube sheetlocations enables the wall-to-wall spacing in the center of the matrixto be determined independently of structural limitations in the spacingof the tubes at the tube sheets.

It will also be evident that the unit is symmetrical in every way andthat the tubes themselves are all identical as to length and shape. Thishas a definite bearing on the cost of making the tube matrix and also onthe characteristics of the fluid flow through the tubes. Further, thedistribution of the shell side fluid is clearly I improved due to thesymmetry of the matrix and due to the fanning of the tubes at the endregions.

It will also be noted in this connection that no part of the mainstructure of the heat exchanger, other than the tubes, has hot liquid onone side and cold on the other, thus minimizing stresses in thestructure.

Making the tube bundle so that it can he slipped axially into a closelyfitted outer shell without the necessity of longitudinal welds in thelatter following the assembly removed some of the most troublesomeproblems in the construction of heat exchangers for veryhigh-temperature fluids. It the longitudinal weld in the outer shell ismade after assembly, the shrinkage in the metal causes a longitudinaldepression, or trough, along the weld which destroys the cylindricalgeometry of the shell and frequently results in burning of one or moretubes in the interior matrix during welding' Also avoiding longitudinalshell welds eliminates long welds which are incapable of inspection andlong loop welds.

Another advantage of the present construction is the support providedfor the tube sheets. These washershaped members are welded to the outercasing and to the header at their outer periphery and to both the headerand the axial flow tube at their inner periphery, resulting in a muchlighter weight tube sheet than would otherwise be possible.

While only one embodiment of the invention has been shown, it will beunderstood that various changes in the construction and arrangement ofthe parts may be made without departing from the invention as defined inthe following claims.

I claim:

1. In a heat exchanger'of counter-fluid-flow configuration, a generallycylindrical tube bundle, the tubes in said bundle being identical asregards length and shape and comprising intermediate straight closelyspaced tubes which extend throughout the major length of the bundle andstraight outwardly offset connected tubes at each end which are parallelwith said intermediate tubes and are more widely spaced, the offsettubes providing an annular axial'chamber reentrant into the bundle ateach end of the tube bundle, an annular tube sheet at each end of saidbundle through which the offset ends of the tubes extend, each of saidtube sheets having a central aperture axially aligned with the adjacentreentrant chamber at its respective end of the tube bundle, an annulartube-side header enclosing the outer side of each tube sheet having acentral aperture axially aligned with the aperture in the adjacent tubesheet, one of said headers 7 comprising an inlet header and having aradial inlet pipe for a first fluid, the other comprising an outletheader and having a radial outlet pipe for said first fluid, an inletpipe for a second fluid extended axially through the central aperture insaid outlet header and through the aligned aperture in said adjacenttube sheet, an outlet pipe for said second fluid extended axiallythrough the central aperture in said inlet header and through thealigned aperture in the adjacent tube sheet, and a cylindrical outercasing enclosing said tube bundle and said tube sheets and secured atits opposite ends to said respective headers.

2. A heat exchanger as defined in claim 1 in which a cylindricalflow-directing liner closely surrounds the intermediate tubes of thebundle and has outwardly directed annular end flanges which engage theouter casing adjacent the ofiset cylindrical tubes.

3. In a heat exchanger, an axial cylindrical tube bundle having anintermediate cylindrical Waist portion made up of straight closelyspaced tubes and having the tubes outwardly offset at their ends to formcylindrical end portions of larger diameter, an annular tube sheet ateach end of said tube bundle through which the ends of the tubes extend,said tube sheets having a large central aperture, an annular tube sideheader enclosing the outer side of each tube sheet having an axialopening aligned with the central aperture in said tube sheets, a fluidinlet for a first fluid communicating with one of said headers, a fluidoutlet for said first fluid communicating with the other'of saidheaders, a cylindrical shell surrounding said tube bundle having adiameter adapted to closely receive the large diameter end portions ofsaid bundle, a cylindrical flow-directing liner closely surrounding theintermediate portion of said, tube bundle and flared at its ends intoengagement with said shell adjacent the offset end portions of saidtubes, and axial inlet and outlet pipes extended into said axialopenings in said respective headers and the central apertures of saidtube sheets and forming the inlet and outlet for a second fluid.

4. In a heat exchanger of the counter-fluid-fiow type, a generallycylindrical tube bundle, said bundle having an intermediate straightcylindrical waist portion in which a plurality of straight tubes areclosely spaced and from which the tubes are outwardly fanned and mergeinto cylindrical end portions of larger diameter in which straight tubesparallel with said intermediate tubes are more widely spaced, an annulartube sheet at each end of said bundle through which the ends of saidtubes extend and by which the spacing of said tubes is determined, saidtube sheets having a central aperture, an annular tube-side headerenclosing the outer side of each tube sheet, each of said headers havingan axial opening, inlet and outlet connections for a first fluid securedin said openings about the central aperture in said tube sheets, aradial outlet connection for the header which has said axial inletconnection and a radial inlet connection for the header which has saidaxial outlet connection, a cylindrical shell surrounding said tubebundle having a diameter adapted to receive closely the larger diameterend portions of said tube bundle, and a cylindrical flow-directing linerclosely surrounding the intermediate portion of said tube bundle, saidliner having its ends flared and engaging the inner annular surface ofsaid shell.

5. In a heat exchanger, a straight tubular casing open at both ends, atube matrix in said casing coextensive with the length of said casing,said matrix at its opposite ends having 'itstubes fanned into an annulusbounded by the tubular casing and forming an axial reentrant corepassage, said tube matrix having an extensive waist portion intermediatethe annuli at its ends in which the tubes are more closely spaced onefrom another and in which said matrix is spaced from said outer casingby a substantial distance, washer-shaped tube sheets at'the ends of saidmatrix having tube apertures through which the tubes in said annuliextend, inlet and outlet headers secured to the opposite ends of saidcasing enclosing said tube sheets and forming a closure for the ends ofsaid casing except for axial flow passages communicating through saidheaders with said axial core passages in the annuli of said matrix,inlet and outlet pipes for a first fluid flow connected to said inletand outlet headers respectively, an axial inlet connection secured in afluid-tight manner to the inner periphery of said outlet header for asecond fluid flow, an axial outlet connection secured in a fluid-tightmanner to the inner periphery of said inlet header for said second fiuidflow, and a flow-directing liner in said casing surrounding the Waistportion of said matrix for directing the path of said second fluid fiowthrough said Waist portion or" said tube matrix.

6. In a heat exchanger, a tubular enclosing casing open at both ends, atube matrix in said casing comprising a bundle of longitudinallyextending tubes having their ends terminating at the ends of saidcasing, the several tubes in said bundle all being of the same lengthand the same shape, said tubes being straight and closely spaced fromone another throughout a major intermediate portion of the length ofsaid casing so that said tube matrix throughout said intermediateportion occupies an am'al position in said casing well spaced from thecasing side wall, the tubes in said straight portion of said tube matrixbeing flared at both ends into short axially extended portions whichform an annulus bounded by the outer casing and by a central annularreentrant passage, the tubes in said annuli being straight and parallelwith the tubes in said intermediate portion, a washer-shaped tube sheetat each end of said matrix having tube apertures through which saidtubes extend, a torus-shaped inlet header for a first fluid how at oneend of said casing enclosing one of said tube sheets having an axialopening aligned with said central annular passage at said end of saidmatrix, an outlet pipe for a second fluid flow secured in said alignedaxial opening of said inlet header, a similar torusshaped outlet headerfor said first fluid flow at the other end of said casing enclosing theother tube sheet, an inlet pipe for said second iluid flow secured inthe axial opening of said outlet header, and inlet and outletconnections for said first fluid in said inlet and outlet headersrespectively.

7. A heat exchanger as defined in claim 6 in which a cylindricalflow-directing liner closely surrounds the intermediate portion of saidtube matrix and has its ends fanned out along the flared tube ends intoengagement with the inside surface of said outer casing, whereby thesecond fluid flow is directed axially along the intermediate straightportion of said tubes.

8. A heat exchanger as defined in claim 7 in which the tubes in theintermediate portion of the tube matrix are supported by at least onetube support assembly consisting of a plurality of annular concentrichoops each of which engages the inner surface of a circular array oftubes.

9. A heat exchanger as defined in claim 7 in which the tubes in theintermediate portion of the tube matrix are supported by at least onetube support assembly consisting of an outer hoop having peripherallyspaced lugs which engage the inner surface of the flow liner and aplurality of concentric split hoops each engaging a circular row of aplurality of concentric rows of tubes, said split hoops each having aplurality of circumierentially spaced radially extending tube supportswhich are secured thereto and extend between adjacent tubes in the rowwhich it supports.

10. A heat exchanger having a straight cylindrical outer shell, acylindrical tube bundle receivable axially in said shell, said bundlehaving a straight cylindrical intermediate portion of considerably lessdiameter than the inner wall of said shell and cylindrical end portionswhich are a close fit in said shell, the tubes in said bundle all beingof the same length and the same shape and each comprising a long,straight intermediate portion and straight outwardly offset end portionsparallel with said intermediate portion which are connected by obliqueportions with said intermediate portion, washer-shaped tube sheets atthe ends of said cylindrical end portions of said bundle havingapertures through which the ol fset ends of said tubes extend, inlet andoutlet headers at opposite ends of said casing each enclosing one of theremote sides of said tube sheets and having inlet and outlet pipesrespectively for the tube-side fluid, and axial inlet and outlet pipesfor the shell-side fluid extended through said headers and through saidtube sheets into said shell.

References Cited in the file of this patent UNITED STATES PATENTS1,852,490 Sullivan Apr. 5, 1932 2,603,457 Bishop July 15, 1952 2,990,162Otten June 27, 1961 3,074,480 Brown et a1. Jan. 22, 1963 FOREIGN PATENTS984,248 France Feb. 21, 1951

1. IN A HEAT EXCHANGER OF COUNTER-FLUID-FLOW CONFIGURATION, A GENERALLYCYLINDRICAL TUBE BUNDLE, THE TUBES IN SAID BUNDLE BEING IDENTICAL ASREGARDS LENGTH AND SHAPE AND COMPRISING INTERMEDIATE STRAIGHT CLOSELYSPACED TUBES WHICH EXTEND THROUGHOUT THE MAJOR LENGTH OF THE BUNDLE ANDSTRAIGHT OUTWARDLY OFFSET CONNECTED TUBES AT EACH END WHICH ARE PARALLELWITH SAID INTERMEDIATE TUBES AND ARE MORE WIDELY SPACED, THE OFFSETTUBES PROVIDING AN ANNULAR AXIAL CHAMBER REENTRANT INTO THE BUNDLE ATEACH END OF THE TUBE BUNDLE, AN ANNULAR TUBE SHEET AT EACH END OF SAIDBUNDLE THROUGH WHICH THE OFFSET ENDS OF THE TUBES EXTEND, EACH OF SAIDTUBE SHEETS HAVING A CENTRAL APERTURE AXIALLY ALIGNED WITH THE ADJACENTREENTRANT CHAMBER AT ITS RESPECTIVE END OF THE TUBE BUNDLE, AN ANNULARTUBE-SIDE HEADER ENCLOSING THE OUTER SIDE OF EACH TUBE SHEET HAVING ACENTRAL APERTURE AXIALLY ALIGNED WITH THE APERTURE IN THE ADJACENT TUBESHEET, ONE OF SAID HEADERS COMPRISING AN INLET HEADER AND HAVING ARADIAL INLET PIPE FOR A FIRST FLUID, THE OTHER COMPRISING AN OUTLETHEADER AND HAVING A RADIAL OUTLET PIPE FOR SAID FIRST FLUID, AN INLETPIPE FOR A SECOND FLUID EXTENDED AXIALLY THROUGH THE CENTRAL APERTURE INSAID OUTLET HEADER AND THROUGH THE ALIGNED APERTURE IN SAID ADJACENTTUBE SHEET, AN OUTLET PIPE FOR SAID SECOND FLUID EXTENDED AXIALLYTHROUGH THE CENTRAL APERTURE IN SAID INLET HEADER AND THROUGH THEALIGNED APERTURE IN THE ADJACENT TUBE SHEET, AND A CYLINDRICAL OUTERCASING ENCLOSING SAID TUBE BUNDLE AND SAID TUBE SHEETS AND SECURED ATITS OPPOSITE ENDS TO SAID RESPECTIVE HEADERS.